In the prototype version of the game, Raidou is given an end card sequence, hinting that he would have been unlockable in the final version.

"Is this the end? ...
I looked down at my opponent who fell at my feet and muttered the thunder track. It's been a long time since you came out to be chasing a village like this or the one Kirigen Tenjinryu. Since then, the thunder road has only sought power for appetite. Fight against all the fighters, made his technique his own. I was asked to be a member of the tournament because I had a feeling that I might be able to meet the hunger for mosquitoes. However, it seems to be useless. The thunder road called a storm and disappeared into the fog..."
Contributed by DrakeVagabond